1. Field of Invention
The invention relates to a breather and in particular to a lamp breather with a waterproof air-permeable membrane.
2. Description of the Prior Art
Outdoor lamps as well as some types of indoor lamps are currently provided with seal rings between the lamp shell and glass or at other connection positions so as to guarantee the mechanical seal performance of the whole lamps. However in case of a great difference between the inner and outer temperatures of the lamp, a great difference between the pressures inside and outside the lamp housing irresistibly exists, which strictly challenges the mechanical seal system of the lamp and brings about a high risk of failure. By way of an example, the difference between the pressures inside and outside a working lamp will increase suddenly due to an abrupt rain and a drop in temperature, thus leading to easy entry of water or dust into the lamp. To address the above problem, a waterproof air-permeable membrane is typically arranged on the lamps so as to permit the passage of air while repelling water or like liquid. For example, expanded polytetrafluoroethylene (ePTFE) developed by General Electric Company in year 2008 can be used as a type of waterproof air-permeable membrane. Such waterproof air-permeable membrane facilitates to balance the pressures inside and outside the lamp housing, and thereby effectively protects the lamp against the sudden change of the outside temperature of the lamp.
Generally, such device equipped with a waterproof air-permeable membrane is referred to as a breather. A problem is that, the breather which is in partial communication with the outer environment can easily fail due to the environmental change. In the case where rain accumulates on the waterproof air-permeable membrane, the breather is prevented from keeping in communication with outside atmosphere and thus out of work.